scholarly journals Efficiency of Hysteresis Rods in Small Spacecraft Attitude Stabilization

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Assal Farrahi ◽  
Ángel Sanz-Andrés
Keyword(s):  
Thin Film ◽  
Cross Section ◽  
Circular Cross Section ◽  
Semiempirical Method ◽  
Spacecraft Attitude ◽  
Flight Data ◽  
Small Satellites ◽  
Attitude Stabilization ◽  
Section Shape ◽  
Good Agreement

A semiempirical method for predicting the damping efficiency of hysteresis rods on-board small satellites is presented. It is based on the evaluation of dissipating energy variation of different ferromagnetic materials for two different rod shapes: thin film and circular cross-section rods, as a function of their elongation. Based on this formulation, an optimum design considering the size of hysteresis rods, their cross section shape, and layout has been proposed. Finally, the formulation developed was applied to the case of four existing small satellites, whose corresponding in-flight data are published. A good agreement between the estimated rotational speed decay time and the in-flight data has been observed.

Study on Special Shaped Polyester Fibers and Development of Products

2021 ◽  
Vol 8 (3) ◽  
pp. 17-22
Author(s):  
Yeqian Ge ◽  
Qin Deyan ◽  
Wang Hongfang ◽  
Tu Jianhong ◽  
Wang Xuefei ◽  
...  
Keyword(s):  
Cross Section ◽  
Natural Fibers ◽  
Great Influence ◽  
Circular Cross Section ◽  
Synthetic Fibers ◽  
Pet Fabric ◽  
Knit Fabrics ◽  
Section Shape ◽  
Pet Fibers ◽  
Profiled Fibers

Non-circular profiled fibers are generally synthetic fibers that have a modified cross-section shape, which are created to mimic natural fibers or to obtain special properties. The shape of the cross-section has great influence on the properties of profiled polyester (PET) fibers and their fabrics. The structure and properties of flat-shaped and hexagonal-shaped profiled PET fibers and ordinary PET fibers, as well as the properties of their knit fabrics were characterized. Experimental results showed that air permeability, heat retention, and wrinkle resilience of profiled PET fabrics were better than that of circular a cross-section PET fiber fabric, while the circular cross-section PET fabric was softer than the profiled PET fiber fabrics.

Modeling the Phonon Transport in Nanowire with Different Cross-Section

2013 ◽  
Vol 401-403 ◽  
pp. 852-855
Author(s):  
Gao Hui Su ◽  
Zi Chun Yang ◽  
Feng Rui Sun
Keyword(s):  
Thermal Conductivity ◽  
Cross Section ◽  
Diffuse Reflection ◽  
Silicon Nanowire ◽  
Circular Cross Section ◽  
Phonon Transport ◽  
Reflection Mode ◽  
Section Shape ◽  
Section Size ◽  
The Cross

The phonon transport in silicon nanowire was simulated by Monte Carlo Method (MCM). The effect on the phonon transport of the boundary reflection mode, cross-section size and cross-section shape was studied. Analysis shows that diffuse reflection can result in phonon accumulation at the circumferential boundary. As the cross-section size decrease, the nonuniformity of the temperature distribution within the cross-section becomes more severe. When the area of the square cross-section silicon nanowire (SCSN) is equal to that of the circular cross-section silicon nanowire (CCSN), the thermal conductivity of them is more close to each other.

Rise in optimized capillary channels

2013 ◽  
Vol 731 ◽  
pp. 142-161 ◽  
Author(s):  
B. Figliuzzi ◽  
C. R. Buie
Keyword(s):  
Cross Section ◽  
Silicone Oil ◽  
Capillary Rise ◽  
Circular Cross Section ◽  
Heat Pipes ◽  
Design And Optimization ◽  
The Subject ◽  
Micro Heat Pipes ◽  
Good Agreement ◽  
Optimal Radius

AbstractMany technological applications rely on the phenomenon of wicking flow induced by capillarity. However, despite a continuing interest in the subject, the influence of the capillary geometry on the wicking dynamics remains underexploited. In numerous applications, the ability to promote wicking in a capillary is a key issue. In this article, a model describing the capillary rise of a liquid in a capillary of varying circular cross-section is presented. The wicking dynamics is described by an ordinary differential equation with a term dependent upon the shape of the capillary channel. Using optimal control theory, we were able to design optimized capillaries which promote faster wicking than uniform cylinders. Numerical simulations show that the height of the rising liquid was up to 50 % greater with the optimized shapes than with a uniform cylinder of optimal radius. Experiments on specially designed capillaries with silicone oil show a good agreement with the theory. The methods presented can be useful in the design and optimization of systems employing capillary-driven transport including micro-heat pipes or oil extracting devices.

Effect of standoff distance and area ratio on the performance of circular exhaust ejector using computational fluid dynamics

2017 ◽  
Vol 232 (15) ◽  
pp. 2821-2832 ◽  
Author(s):  
L Singh ◽  
SN Singh ◽  
SS Sinha
Keyword(s):  
Fluid Dynamics ◽  
Reynolds Number ◽  
Cross Section ◽  
Circular Cross Section ◽  
Area Ratio ◽  
Standoff Distance ◽  
Tube Length ◽  
Mass Entrainment ◽  
Section Shape ◽  
Ejector Nozzle

Numerical investigation is carried out to study the effect of standoff distance and area ratio on mass entrainment of an air–air circular exhaust ejector. Nozzle and mixing tube are the two components of an ejector, and for the present study, circular cross section shape has been chosen. Numerical simulations have been carried out at Reynolds number in the range of 6.85 × 104 and 4.11 × 105. Area ratio is varied between 1.25 < area ratio < 4 and standoff distance is varied from 1 Dnz < standoff distance < 4 Dnz, where Dnz represent the nozzle exit diameter. It is observed that for the ejector configuration with area ratio as 2, 2.25, and 2.5, the mass entrainment characteristics are nearly independent of standoff distance between 1 Dnz to 4 Dnz. For ejector configuration with area ratio below 2, mass entrainment decreases with increase in standoff distance. For ejector configuration with area ratio greater than 2.5, mass entrainment increases with increase in standoff distance for the range investigated and has the tendency to taper off beyond 4 Dnz for most of the area ratios. Effect of change in mixing tube length is also studied. It is seen that the mass entrainment improves with increase in length up to 8 Dnz. Further increase in length does not effect mass entrainment. This study provides important guidelines that can aid in arriving at an optimal design of circular exhaust ejectors.

Spirally bound concrete columns

1985 ◽  
Vol 400 (1818) ◽  
pp. 127-144 ◽  
Keyword(s):  
Cross Section ◽  
Material Properties ◽  
Circular Cross Section ◽  
Plain Concrete ◽  
Concrete Columns ◽  
Stress Strain Relation ◽  
Mathematical Expressions ◽  
Iterative Procedures ◽  
Theoretical Results ◽  
Good Agreement

In this paper, mathematical expressions for the material properties of plain concrete are used in conjunction with the stress–strain relation of steel reinforcement to develop equations for both the strength and deformational behaviour of axially loaded concrete columns of circular cross section and with closely spaced spiral binding. Iterative procedures are used to solve these equations and the theoretical results are shown to be in good agreement with experimental results obtained by earlier investigators.

Effect of contributions from bending in evaluation of axial strain in rods with circular cross-section

1983 ◽  
Vol 18 (1) ◽  
pp. 77-79 ◽  
Author(s):  
L Lagerkvist ◽  
K-G Sundin ◽  
B Lundberg
Keyword(s):  
Cross Section ◽  
Axial Strain ◽  
Circular Cross Section ◽  
Strain Gauges ◽  
Elastic Rod ◽  
Simple Method ◽  
Strain Measurements ◽  
Absolute Value ◽  
Bending Strain ◽  
Good Agreement

Contributions from bending to the evaluated axial strain in an elastic rod are commonly suppressed by forming half the sum of measured surface strains at diametrically opposite positions. A simple method is presented which gives a useful estimation of the bending suppression (the ratio of the bending strain to the absolute value of the evaluated axial strain when a rod is subject to bending only) from (i) optically measured mis-positioning, and (ii) estimated differences between the gauge constants for the two strain gauges. Good agreement is obtained with results obtained from strain measurements on a rod loaded in bending.

scholarly journals Calculation of eigen frequency splitting of a cylindrical resonator of a solid-state wave gyroscope based on numerical integration of high accuracy

2019 ◽  
Author(s):  
O.S. Narajkin ◽  
F.D. Sorokin ◽  
A.M. Guskov ◽  
S.A. Kozubnyak ◽  
D.S. Vahlyarskiy
Keyword(s):  
Solid State ◽  
Angular Velocity ◽  
Cross Section ◽  
Circular Cross Section ◽  
High Accuracy ◽  
Cylindrical Resonator ◽  
Frequency Splitting ◽  
State Wave ◽  
Cross Section Shape ◽  
Section Shape

Solid-state wave gyroscopes are widely used in various fields of technology. The principle of their operation is based on the phenomenon of precession of the elastic wave, which rotates at an angular velocity proportional to the angular velocity of device body rotation. The accuracy of the device is significantly affected by splitting the gyroscope resonator frequency. The article considers splitting caused by the distortion of the cylindrical resonator cross-section shape. Since the splitting is very small, the perturbation method is usually used to determine it. The article proposes a new method for calculating the splitting based on the numerical high accuracy integration of equations of dynamics of a cylindrical shell with a non-circular cross section. To search for two very close frequencies, through the difference of which the splitting was found, a linear boundary eigenvalue problem was solved with retention of a large number of decimal places. Examples of determining the natural frequency splitting are presented for various laws of the distribution of the radial deviation of the cavity cross-section shape along the circumferential coordinate. Verification of the results was performed by the finite element method. When using the method each of the two close frequencies was calculated with high accuracy

The Line Contact Between Two Cylinders—Some Experiments and Theoretical Predictions

1988 ◽  
Vol 110 (2) ◽  
pp. 285-291 ◽  
Author(s):  
J. M. de Mul ◽  
H. van Engelenburg
Keyword(s):  
Half Space ◽  
Cross Section ◽  
Circular Cross Section ◽  
Infinite Cylinder ◽  
Space Model ◽  
Linear Elastic ◽  
Cylinder Model ◽  
Theoretical Predictions ◽  
Frictional Effects ◽  
Good Agreement

Experiments are presented in which various combinations of two (almost) straight cylinders with circular cross-section are pressed together while their axes remain basically parallel. Results are compared with theoretical predictions from a half space model; from this half space model extended with adjustments for the finite dimensions of the cylinders in contact; and from an infinite cylinder model from literature. Frictional effects are not considered and the material is assumed to be linear-elastic. Agreement in the approach of the center lines of the cylinders under load is found to exist more or less between the experimental results and the theoretical predictions by the models. The behaviour of the models is discussed, and reasonable to good agreement is demonstrated for the extended half space model using an integral depth adjustment of 3/4 of the diameter of each cylinder in contact. A possible way to further improve this model is indicated.

scholarly journals Study on Crush Tube Geometric Cross sections and Topology for Axial Crashworthiness

2020 ◽  
Vol 70 (3) ◽  
pp. 249-259
Author(s):  
T.J. Reddy ◽  
V. Narayanamurthy ◽  
Y.V.D. Rao
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Circular Cross Section ◽  
Road Vehicles ◽  
Element Analysis ◽  
Impact Forces ◽  
Axial Crush ◽  
Section Shape ◽  
Energy Absorbing ◽  
Initial Peak

Crush tubes are used as crash impact energy absorbing structure (EAS) and are located in the frontal compartment of road vehicles. Ideal crashworthiness of an EAS mandates that the equivalent decelerations due to impact forces should to be ≤ 20g; and crush force and stroke efficiencies should tend to unity. It is understood from the literature that no single geometric cross-section shape exhibits a near-ideal crashworthiness; and most EAS members exhibit a high initial peak crush force which is detrimental to the occupant safety, and moderate stroke and crush force efficiencies leading to a compromise in the total energy absorbed. In this paper, finite element analysis (FEA) methodology is formulated and experimentally validated for axial crush of a crush tube of SS304 material with circular cross section.  Subsequently, plastic deformation phenomenon and folding patterns in relation to crush force behaviour of crush tubes with various basic cross-sections of polygonal geometric shapes from triangle to octagon and circle are extensively studied through FEA. Further, two new geometric cross-section profiles with combination of basic shapes are proposed to combine the merits of different basic shapes. The crashworthiness of all basic cross-sections including the two proposed cross-section profiles is assessed based on standard parameters. The proposed new geometries may form a basis for the development of new EAS configurations for enhanced crashworthiness.

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